Nuisance fuse operation on MV transformers during storms

The authors report on producing in a laboratory a sequence of events leading to nuisance operation of fuses on distribution transformers during thunderstorms. It is observed that such nuisance operations can be caused by long (a few milliseconds) low-amplitude (less than 1 KA) current passing through a surge arrester, causing overvoltage and saturation of its protected transformer and an inrush current that blows the fuse without a fault situation. An experimental sensitivity analysis was performed by varying the surge arrester, transformer, and fuse involved. In general, new ZnO-based arresters, which produce a higher voltage than SiC-based arresters at impulse currents below 1000 A, will result in a higher transformer inrush current and greater likelihood of nuisance fuse blowing